Satellitenbasierte Analyse der Luftverschmutzung durch Stickstoffdioxid: von globalen zu urbanen Aspekten

Kurzfassung

Air pollution is globally recognized as the most significant environmental health risk, disproportionately affecting urban populations. Moreover, air pollutants impact climate, ecosystems, and economies. Traditionally, air pollutants have been monitored through spatially scattered in-situ measurement stations providing localized information. However, satellite-based Earth Observation has enabled global, continuous, and spatially homogenous monitoring of air pollution since 1996. This dissertation comprises three studies employing satellite data to analyze and assess the spatiotemporal distribution and dynamics of nitrogen dioxide (NO2) air pollution at various spatial scales (global, national, regional, urban). Given its short atmospheric lifetime and primarily anthropogenic origin, NO2 was used as an indicator of air quality and anthropogenic activity patterns. The first study investigated the statistical relationship between urban growth and tropospheric NO2 pollution trends for 38 megacities worldwide from 1996 to 2015. Satellite data from GOME, SCIAMACHY, GOME-2A, and GOME-2B, alongside settlement growth data from the World Settlement Footprint Evolution, were utilized. This study, for the first time, systematically identified correlations between urban growth and NO2 trends using a consistent spatial delineation of megacities by applying the concept of Functional Urban Areas. An average annual increase in tropospheric NO2 concentrations of 5.06 ± 0.83% was found, with settlement growth averaging 2.87% per year. It was revealed that the relationship between NO2 burden and urban expansion was significantly influenced by the World Bank's socioeconomic income classification, with higher NO2 growth in rapidly expanding cities. Thus, the study advances beyond previous research by providing a deeper understanding of the development trajectories of megacities and their implications for global health and sustainability. The second study focused on Germany, employing satellite data from Sentinel-5P/TROPOMI at unprecedented spatial resolution (3,5 km x 5,5 km) and Sentinel-2 data, to analyze national spatial patterns of NO2 pollution and its determinants. Through coldspot and hotspot analyses, 24 national hotspots were identified, predominantly located in urban areas but also in energy-intensive regions. A location-specific analysis of influencing factors consistently identified impervious surfaces, population density, and road density as dominant determinants of NO2 pollution levels across all regions, whereas other factors had more location-specific impacts. These findings underscore the sensitivity of TROPOMI to pollutants in the boundary layer and the potential of high-resolution satellite-based Earth Observation data to detect and analyze complex environmental geographic relationships. The third study examined the regional effects of a NOx emission tax introduced in the Comunidad Valenciana, Spain, in 2013, using a difference-in-differences approach combined with multi-temporal satellite-based NO2 data. Results showed that the tax led to a moderate yet significant annual NO2 reduction of 1.2%, corresponding to an emission decrease of approximately 728 tons of NOx. Additional analyses indicated stronger effects in industrial regions, technologically innovative firms, and larger companies. Conversely, firms with substantial market power partially shifted the tax burden, diminishing the environmental effectiveness of the tax. These findings highlight the necessity of complementing emission taxes with additional regulatory measures and innovation incentives. Collectively, these studies confirmed and expanded the fundamental hypothesis, illustrating a nonlinear relationship between air pollution and economic development following an inverted U-shaped curve (Environmental Kuznets Curve, EKC). According to this model, environmental pollution initially increases in early economic development stages, peaks at intermediate income levels, and subsequently declines with further economic prosperity. Thus, the presented research significantly contributes to environmental geography and environmental policy by revealing spatial patterns, temporal dynamics, driving factors, and potential policy actions for sustainably improving air quality. In summary, the contributions of this dissertation demonstrate that satellite-based Earth Observation of air pollution and urbanization, especially when integrated with complementary geospatial datasets such as socioeconomic indicators, economic metrics, and land cover information, provides a robust framework for comprehensively monitoring environmental dynamics. Furthermore, the insights gained offer decision-makers reliable and evidence-based guidance essential for the design of targeted, effective, and sustainable environmental policies and interventions.